Light-collimating plastic films, sometimes known as light control film, are well-known in the art. Such films typically have opaque plastic louvers lying between strips of clear plastic. U.S. Pat. No. Re 27,617 (Olsen) teaches a process of making such a louvered light control film by skiving a billet of alternating layers of plastic having relatively low and relatively high optical densities. After skiving, the high optical density layers provide light-collimating louver elements which, as illustrated in the patent, may extend orthogonally to the surface of the resulting louvered plastic film. U.S. Pat. No. 3,707,416 (Stevens) discloses a process whereby the light-collimating louver elements may be canted respect to the surface of the light control film. U.S. Pat. No. 3,919,559 (Stevens) teaches a process for attaining a gradual change in the angle of cant of successive light-collimating louver elements.
Such light-collimating films have many uses. U.S. Pat. No. 3,791,722 (Ahlberg et al.) teaches the use of such films in lenses for goggles to be worn where high levels of illumination or glare are encountered. Such films also may be used to cover a back-lighted instrument panel, such as the dashboard of a car, to prevent undesired reflections in locations such as the windshield. A louvered plastic film may also be used to give a black and white photographic negative the appearance of a positive made from the negative, as taught in U.S. Pat. No. 3,653,138 (Cooper). U.S. Pat. No. 3,922,440 (Wegwerth et al.) teaches that because louvered plastic films "are thin sheet materials: (1) they are not by themselves capable of structurally withstanding extreme stresses and (2) they are subject to distortion from physical stress and temperatures" (Col. 1, lines 19-22). This physical weakness is particularly pronounced because the films are composite products made from alternating layers of different materials. Furthermore, the skiving by which the louvered plastic films are produced results in irregular surfaces. Such irregular surfaces prevent the skived plastic films from transmitting a clear optic image. Accordingly, the Wegwerth et al. patent teaches the lamination of clear plastic films on each side of the skived louvered film. These clear plastic films provide protection and support as well as an optically-smooth surface.
The process of laminating louvered plastic films between two clear films requires an expensive press that is also expensive to operate. The expense results, in part, from the need to distribute heat uniformly and, in part, from the need to apply pressure with precision. Because the resulting laminates cannot be larger than the platens of the press in which they are laminated, the press must be sufficiently large to produce the largest required size, thus increasing the expense of the press.